1. Field of the Invention
The present invention relates to an Fe-based soft magnetic alloy suitable as materials for use in magnetic cores of various transformers and saturable reactors, various choke coils, various magnetic heads and the like and suitable as magnetic materials for use in various sensors and the like and a method of producing the same.
2. Description of the Related Art
For example, conventionally used as the magnetic materials for various magnetic parts in power supplies and magnetic heads have been mainly Permalloy, Fe-Al-Si alloy, silicon steel, ferrite and the like.
Meanwhile, there have been increasing demands for miniaturization, higher efficiency and the like of electronic equipment and appliances in recent years and, for example switching frequencies of power supplies have been and will be a high frequency in order to meet these requirements. It thus has been desired that the magnetic materials constituting magnetic parts should have improved properties such as low iron loss, high saturation magnetic flux density and the like in the high frequency region.
The above-mentioned materials, however, are not satisfactory as regards these requirements. Amorphous alloys thus have attracted attention recently in their role of the soft magnetic materials meeting the requirements associated with high frequency.
Amorphous alloys show the excellent soft magnetic properties such as high permeability, low coercive force and the like. They also have the properties of low iron loss, high squareness ratio and the like at high frequency. Because of these advantages some of amorphous alloys practically have been used as the magnetic material for switching power supplies. For example, Co-based amorphous alloys have been used for saturable reactors and the like, while Fe-based amorphous alloys for choke coils and the like.
These amorphous alloys also have many problems to solve, however. For example, Co-based amorphous alloys exhibit the excellent properties, having low iron loss, high squareness ratio and the like in the high frequency region. On the other hand, however, they have the disadvantage that they are comparatively high priced and less likely to find wide prevalent use. Fe-based amorphous alloys are reasonably priced and eligible for wide prevalent use. On the other hand, however, they have the disadvantage that they don't acquire zero magnetostriction, their magnetic properties are susceptible to large deterioration due to stress by setting constraction of resin at the time of resin molding and the like and there is a high incidence of noises associated with magnetostriction vibration.
Meanwhile, Fe-based soft magnetic alloys having precipitated super fine crystal grains and the soft magnetic properties comparable to those of Co-based amorphous alloys have been proposed recently (cf. Japanese Patent Laid Open No. 320504/1988). These Fe-based soft magnetic alloys have the excellent soft magnetic properties but also the advantages described below. That is, Since they have low magnetostriction and they are based on Fe, their price is on a comparatively reasonable level. Because of these advantages Fe-based soft magnetic alloys have attracted attention as a magnetic material to replace Co-based amorphous alloys.
However, the above-mentioned Fe-based soft magnetic alloys had a weakness that their magnetic properties have large dependence on the heat treatment temperatures during their production process. That is, in the above-mentioned Fe-based soft magnetic alloys, alloy matrices are once made amorphous and then heat-treated in a range of temperatures close to the crystalization temperature in order to precipitate fine crystal grains. The excellent magnetic properties are generated with precipitation of said fine crystal grains. The range of optimum heat treatment temperatures is narrow, however. Furthermore, a very large amount of energy is discharged at the time crystalization occurs from the amorphous state. These make it highly likely that the heat treatment temperature in the production steps exceeds the prescribed range of temperatures. When the heat treatment temperature exceeds the prescribed range, coarse crystal grains are liable to precipitate and the above-mentioned excellent magnetic properties cannot be obtained.